The invention relates to a wet-running multi-disc brake having stator discs which are arranged in parallel and at a spacing from one another. The stator discs are held in a rotationally fixed manner. Between the stator discs in each case, one rotatable rotor disc is positioned. During a braking operation, the radially extending stator discs and rotor discs are pressable against one another by way of a brake application device while overcoming a clearance gap.
In comparison with dry-running brakes, for example disc brakes, as have been used up to now predominantly in road vehicles, in particular in heavy commercial vehicles such as road trucks and buses, wet-running multi-disc brakes afford advantages in relation to robustness, service life of the brake pads and environmental pollution.
Conventional dry-running friction brakes are subject to relatively high wear and produce brake abrasion, which contributes to a not inconsiderable amount of dust pollution, in particular fine dust pollution of the environment.
Moreover, the brake pad wear requires corresponding maintenance work which causes additional operating costs.
In contrast, wet-running multi-disc brakes have been used up to now principally in special trucks, heavy construction vehicles, tractors or the like; said wet-running multi-disc brakes are subject to very low wear and are operated at a low temperature level.
The wet-running brakes are usually actuated hydraulically, while dry-running multi-disc brakes which are likewise used, for example, in said special trucks, are actuated, for example, pneumatically or mechanically.
In order to reduce the actuating force, self-energizing devices are provided in such dry-running multi-disc brakes, which self-energizing devices have an actuating ring with ramps which extend on one side in the rotational direction of the rotor discs. Via the actuating ring, firstly the brake application force is transmitted and, secondly, a self-energizing effect is generated.
However, the self-energizing brake application device has to be actuated in a manner which is dependent on the rotational direction, which would be possible in the case of compressed air actuation, for example, by use of two actuating cylinders or a switchover gear mechanism and a rotational direction detection device (and a correspondingly complicated controller). However, a design of this type is not readily suitable for large volume mainly for cost reasons.
Moreover, considerable problems also arise during operation in the case of use in a road vehicle, for example if the corresponding vehicle is braked during an ascent.
Here, the service brake operation takes place until the vehicle reaches a standstill in the forward driving direction. However, the subsequent holding action has to be applied in the backward driving direction in accordance with the direction of the slope effect. As a consequence, this means a greatly reduced braking and holding action in the backward driving direction or, if the ramps are formed in both driving directions, a temporarily unbraked state of the vehicle in the case of a change from the forward to the backward braking direction.
The known mechanical ramp actuating systems do not meet the many requirements of modern commercial vehicle brake systems which, moreover, are known only as dry-running multi-disc brakes, but not as wet-running multi-disc brakes.
The invention is based upon developing further a wet-running multi-disc brake such that its capability to be used is improved, and that it can be used, in particular, in road vehicles.
According to the invention, a wet-running multi-disc brake is provided having stator discs which are arranged in parallel and at a spacing from one another. The stator discs are held in a rotationally fixed manner. Between the stator discs in each case, one rotatable rotor disc is positioned. During a braking operation, the radially extending stator discs and rotor discs are pressable against one another by way of a brake application device while overcoming a clearance gap. The brake application device is actuatable mechanically and acts via an actuating unit on a self-energizing device which has a thrust ring which, during a braking operation, is pressable toward the rotor discs independently of the rotational direction of the rotor discs.
The brake application device can therefore be actuated mechanically for the first time with simultaneous self-energizing, to be precise in both rotational directions of the rotor discs.
First of all, the invention is distinguished by its extremely simple and therefore robust design, since additional measures can be dispensed with, such as the two actuating cylinders already mentioned with respect to the prior art in a pneumatically actuable brake application device or a rotational direction detection means and an associated controller.
The advantages of a mechanically actuable brake application device can therefore be utilized in a wet-running multi-disc brake, without restrictions on the braking behavior during backward driving.
As a result of the self-energizing device, a high application force can be achieved with a low requirement of actuating energy which, as has been shown, is merely from 30 to 50% of the requirement of a conventional brake actuation mechanism.
This leads to a reduction in the necessary frictional contacts and therefore to a reduction in the overall length of the entire brake and minimization of the dimensions of the actuating components such as the brake cylinder, accumulator spring, etc. This facilitates substantial assembly ease in the very constricted installation conditions, in particular in the case of an installation in the region of the front axle.
The actuating unit has an actuating ring which can preferably be adjusted axially via an integrally formed ramp during actuation of the brake application device, that is to say, of an actuator. Here, the ramp is oriented on one side in a rotational direction of the rotor discs, in accordance with the actuating direction of the actuator.
In contrast, the separate thrust ring has two ramp pairs which are oriented in opposite directions in both rotational directions of the rotor discs and correspond with a rolling body which is held in a brake housing such that it can roll but is stationary.
In the region of its respective ramp, the actuating ring is likewise supported on a rolling body which is mounted in a depression of the brake housing.
The parallel connection realized in this way of actuation firstly and self-energizing secondly makes an automatic rotational direction adaptation of the self-energizing without braking force interruption and mutually independent dimensioning of the actuating and energizing ramps possible. The actuating ring and the thrust ring are arranged parallel to one another and lie on one another in a manner which is supported by antifriction bearings.
The actuating ring can therefore introduce its brake application movement and therefore the loading force generated in the case of a braking operation into the thrust ring independently of a rotational movement of the latter.
The thrust ring is provided with a friction face which, in the case of a brake application operation, is pressed by way of the actuating ring against an associated rotor disc which forms a brake disc.
Here, a restoring force which acts before the brake disc assembly and the multi-disc assembly are pressed together and, therefore, before a build up of loading force, and which is generated by restoring springs which are arranged between the stator discs and the thrust ring, is sufficient to generate a frictional force which acts in the circumferential direction on the thrust ring and rotates the thrust ring so far that its ramps are activated in the correct rotational direction.
In the case of a further actuation of the brake, the build up of loading force then takes place. The force which is generated by the ramps of the actuating ring firstly and of the thrust ring secondly acts on the brake disc/multi-disc assembly in a manner which is combined in the thrust ring and as an overall loading force.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.